/*
 * Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.xml.soap;

import java.io.*;
import java.util.Properties;


class FactoryFinder {

  /**
   * Creates an instance of the specified class using the specified
   * <code>ClassLoader</code> object.
   *
   * @throws SOAPException if the given class could not be found or could not be instantiated
   */
  private static Object newInstance(String className,
      ClassLoader classLoader)
      throws SOAPException {
    try {
      Class spiClass = safeLoadClass(className, classLoader);
      return spiClass.newInstance();

    } catch (ClassNotFoundException x) {
      throw new SOAPException("Provider " + className + " not found", x);
    } catch (Exception x) {
      throw new SOAPException("Provider " + className + " could not be instantiated: " + x, x);
    }
  }

  /**
   * Finds the implementation <code>Class</code> object for the given
   * factory name, or null if that fails.
   * <P>
   * This method is package private so that this code can be shared.
   *
   * @param factoryId the name of the factory to find, which is a system property
   * @return the <code>Class</code> object of the specified message factory; or <code>null</code>
   * @throws SOAPException if there is a SOAP error
   */
  static Object find(String factoryId)
      throws SOAPException {
    return find(factoryId, null, false);
  }

  /**
   * Finds the implementation <code>Class</code> object for the given
   * factory name, or if that fails, finds the <code>Class</code> object
   * for the given fallback class name. The arguments supplied must be
   * used in order. If using the first argument is successful, the second
   * one will not be used.
   * <P>
   * This method is package private so that this code can be shared.
   *
   * @param factoryId the name of the factory to find, which is a system property
   * @param fallbackClassName the implementation class name, which is to be used only if nothing
   * else is found; <code>null</code> to indicate that there is no fallback class name
   * @return the <code>Class</code> object of the specified message factory; may be
   * <code>null</code>
   * @throws SOAPException if there is a SOAP error
   */
  static Object find(String factoryId, String fallbackClassName)
      throws SOAPException {
    return find(factoryId, fallbackClassName, true);
  }

  /**
   * Finds the implementation <code>Class</code> object for the given
   * factory name, or if that fails, finds the <code>Class</code> object
   * for the given default class name, but only if <code>tryFallback</code>
   * is <code>true</code>.  The arguments supplied must be used in order
   * If using the first argument is successful, the second one will not
   * be used.  Note the default class name may be needed even if fallback
   * is not to be attempted, so certain error conditions can be handled.
   * <P>
   * This method is package private so that this code can be shared.
   *
   * @param factoryId the name of the factory to find, which is a system property
   * @param defaultClassName the implementation class name, which is to be used only if nothing else
   * is found; <code>null</code> to indicate that there is no default class name
   * @param tryFallback whether to try the default class as a fallback
   * @return the <code>Class</code> object of the specified message factory; may not be
   * <code>null</code>
   * @throws SOAPException if there is a SOAP error
   */
  static Object find(String factoryId, String defaultClassName,
      boolean tryFallback) throws SOAPException {
    ClassLoader classLoader;
    try {
      classLoader = Thread.currentThread().getContextClassLoader();
    } catch (Exception x) {
      throw new SOAPException(x.toString(), x);
    }

    // Use the system property first
    try {
      String systemProp =
          System.getProperty(factoryId);
      if (systemProp != null) {
        return newInstance(systemProp, classLoader);
      }
    } catch (SecurityException se) {
    }

    // try to read from $java.home/lib/jaxm.properties
    try {
      String javah = System.getProperty("java.home");
      String configFile = javah + File.separator +
          "lib" + File.separator + "jaxm.properties";
      File f = new File(configFile);
      if (f.exists()) {
        Properties props = new Properties();
        props.load(new FileInputStream(f));
        String factoryClassName = props.getProperty(factoryId);
        return newInstance(factoryClassName, classLoader);
      }
    } catch (Exception ex) {
    }

    String serviceId = "META-INF/services/" + factoryId;
    // try to find services in CLASSPATH
    try {
      InputStream is = null;
      if (classLoader == null) {
        is = ClassLoader.getSystemResourceAsStream(serviceId);
      } else {
        is = classLoader.getResourceAsStream(serviceId);
      }

      if (is != null) {
        BufferedReader rd =
            new BufferedReader(new InputStreamReader(is, "UTF-8"));

        String factoryClassName = rd.readLine();
        rd.close();

        if (factoryClassName != null &&
            !"".equals(factoryClassName)) {
          return newInstance(factoryClassName, classLoader);
        }
      }
    } catch (Exception ex) {
    }

    // If not found and fallback should not be tried, return a null result.
    if (!tryFallback) {
      return null;
    }

    // We didn't find the class through the usual means so try the default
    // (built in) factory if specified.
    if (defaultClassName == null) {
      throw new SOAPException(
          "Provider for " + factoryId + " cannot be found", null);
    }
    return newInstance(defaultClassName, classLoader);
  }

  /**
   * Loads the class, provided that the calling thread has an access to the
   * class being loaded. If this is the specified default factory class and it
   * is restricted by package.access we get a SecurityException and can do a
   * Class.forName() on it so it will be loaded by the bootstrap class loader.
   */
  private static Class safeLoadClass(String className,
      ClassLoader classLoader)
      throws ClassNotFoundException {
    try {
      // make sure that the current thread has an access to the package of the given name.
      SecurityManager s = System.getSecurityManager();
      if (s != null) {
        int i = className.lastIndexOf('.');
        if (i != -1) {
          s.checkPackageAccess(className.substring(0, i));
        }
      }

      if (classLoader == null) {
        return Class.forName(className);
      } else {
        return classLoader.loadClass(className);
      }
    } catch (SecurityException se) {
      // (only) default implementation can be loaded
      // using bootstrap class loader:
      if (isDefaultImplementation(className)) {
        return Class.forName(className);
      }

      throw se;
    }
  }

  private static boolean isDefaultImplementation(String className) {
    return MessageFactory.DEFAULT_MESSAGE_FACTORY.equals(className) ||
        SOAPFactory.DEFAULT_SOAP_FACTORY.equals(className) ||
        SOAPConnectionFactory.DEFAULT_SOAP_CONNECTION_FACTORY.equals(className) ||
        SAAJMetaFactory.DEFAULT_META_FACTORY_CLASS.equals(className);
  }
}
